5.7.12.9 Pcc-struct-return Option

The -fpcc-struct-return option forces the compiler to return small struct and union objects (whose size and alignment match that of an integer type) in memory, rather than in registers. This convention is less efficient but allows compatibility with files compiled using other compilers.

The -fno-pcc-struct-return form of this option returns small struct and union objects in registers. This is the default action no option is specified.